The present invention relates to an isoflavone enriched vegetable protein isolate and a process for producing the same.
Isoflavones occur in a variety of leguminous plants and oilseeds, including vegetable protein materials such as soybeans. These compounds, for purposes of the present invention, generally include daidzin, 6"-OAc daidzin, 6"-OMal daidzin, daidzein, genistin, 6"-OAc genistin, 6"-OMal genistin, genistein, glycitin, 6"-OMal glycitin, glycitein, biochanin A, and formononetin. As used herein, "Mal" represents "malonyl" and "Ac" represents "acetyl". The structures of these isoflavones are shown in Formulas 1 and 2 below. ##STR1##
______________________________________ Compound R.sub.1 R.sub.2 R.sub.3 R.sub.4 ______________________________________ Genistein OH H OH OH Daidzein OH H H OH Glycitein OH OCH.sub.3 H OH Biochanin A OH H OH OCH.sub.3 Formononetin OH H H OCH.sub.3 ______________________________________ ##STR2##
______________________________________ Compound R.sub.1 R.sub.2 R.sub.3 R.sub.4 ______________________________________ Genistin H H OH OH 6"-OMal genistin COCH.sub.2 CO.sub.2 H H OH OH 6"-OAc genistin COCH.sub.3 H OH OH Daidzin H H H OH 6"-OMal daidzin COCH.sub.2 CO.sub.2 H H H OH 6"-OAc daidzin COCH.sub.3 H H OH Glycitin H OCH.sub.3 H OH 6"-OMal glycitin COCH.sub.3 OCH.sub.3 H OH ______________________________________
It has recently been recognized that the isoflavones contained in vegetable proteins such as soybeans may inhibit the growth of human cancer cells, such as breast cancer cells and prostate cancer cells, as described in the following articles: "Genistein Inhibition of the Growth of Human Breast Cancer Cells: Independence from Estrogen Receptors and the Multi-Drug Resistance Gene" by Peterson and Barnes, Biochemical and Biophysical Research Communications, Vol. 179, No.1 p. 661-667, Aug. 30, 1991; Genistein and Biochanin A Inhibit the Growth of Human Prostate Cancer Cells but not Epidermal Growth Factor Receptor Tyrosine Autophosphorylation" by Peterson and Barnes, The Prostate 22: 335-345 (1993); and "Soybeans Inhibit Mammary Tumors in Models of Breast Cancer" by Barnes et al. Mutagens and Carcinogens in the Diet p. 239-253 (1990). These isoflavones also have been found to reduce cardiovascular risk factors, for example by reducing the levels of atherosclerosis inducing lipoproteins and low density cholesterol and by increasing endothelial dependent vasodilation response.
Typically these isoflavone compounds have been associated with an inherent, bitter flavor in vegetable protein materials such as soybeans. In the commercial production of such protein materials, such as protein isolates and protein concentrates, the focus has been to remove these isoflavone compounds. For example, in a conventional process for the production of a soy protein isolate, soy flakes are extracted with an aqueous medium having a pH above the isoelectric point of the protein to solubilize the protein. The extract containing the protein is separated from insoluble fiber materials to provide a protein extract. The isoflavones are solubilized in the extract as well as the protein. The protein is precipitated by adjusting the pH of the extract to about the isoelectric point of the protein with an acid. The precipitated protein is then separated from the extract. Much of the isoflavones remain solubilized in the extract following separation of the precipitated protein (curd) from the extract. After separation of the precipitated protein curd from the extract, the extract and the isoflavones solubilized therein are usually discarded. Residual isoflavones left in the separated protein are usually removed by exhaustive washing of the protein to ensure that the taste associated with the isoflavones is not present in the protein.
It is desirable, however, to provide an isoflavone rich protein material, and a process for producing the same, which is suitable for administration in a diet. Such an isoflavone rich protein material can be used to provide the nutritional benefits of the protein and the health benefits of the isoflavones when administered in a diet.